1. Field of the Invention
The present invention relates to handheld through-wall sensing systems and, more particularly toward through-wall sensing using wireless and cellular network signals.
2. Description of the Related Art
Conventional handheld systems for through-wall detection are usually based on the use of specialized radiation, such as radar or terahertz waves, which are beamed through a target wall so that the presence and location of any objections on the other side of the wall may be determined based on the returned signals. Such approaches require sophisticated transmission antenna and processing equipment that can reveal the presence of the user of the system.
Other systems rely on the use of existing radiofrequency signals, such as wireless internet or cellular transmissions, which may already be present inside a location. Although these systems are useful for inferring the presence and location of objects within the location based on the effect on the existing transmissions, these systems are passive and thus depend on the presence of an active transmitter within the location to be interrogated.